Recent years have witnessed intense interest and expanding usage of wind turbine systems that convert wind energy to electricity. Wind farms made of scores and even hundreds of such systems are taking over open expanses of land in the U.S. and elsewhere in the world at an increasing rate. Also, individual wind turbine systems are growing in popularity for businesses and homes in high-wind regions. Laws in many states have been passed to promote usage of wind turbine systems.
These systems typically include a tower, a horizontal-axis wind turbine, and an electric generator. The tower extends vertically from the ground and has a top portion supporting the horizontal-axis wind turbine. The horizontal-axis wind turbine has blades like airplane propellers that are fixed to a horizontal shaft, and coupled to the electric generator. In operation, sufficient wind rotates the blades and the shaft, which in turn rotates the electric generator to produce electricity.
The present inventor has recognized several problems with conventional horizontal-axis wind turbine systems. For example, these systems are generally unsuitable for densely populated urban landscapes because they require extensive space for their installation and operation, and are frequently regarded as unsightly and noisy. Moreover, many urban and suburban as well as industrial regions lack the high average wind speeds necessary to make conventional systems economically viable. Additionally, conventional systems are fixed-capacity systems that are not designed to be expanded or adapted to meet changing conditions, such as increased energy needs.
Accordingly, the present inventor has recognized unmet needs for commercially viable wind turbine systems that are suitable for more densely populated regions, that are effective in regions having lower average wind speeds, and that are visually appealing, quieter, and expandable.